Reflector lamp

ABSTRACT

A reflector lamp is described which consist essentially of a light source, in particular in the form of a high-pressure gas discharge lamp (HID [high intensity discharge] lamp or UHP [ultra high performance] lamp), as well as a main or secondary reflector ( 12 ), and a primary reflector ( 25 ) by means of which light from the light source ( 22 ) can be reflected through the light source ( 22 ) onto the main reflector ( 12 ). The primary reflector ( 25 ) is arranged such that those regions of the main reflector ( 12 ) are obscured which are optically inactivated regions, for example because of a lead-through and/or a fastening device for the lamp, which have no reflection properties, or which have reflection properties that adversely affect the radiation characteristic of the reflector lamp. The reflector lamp is particularly suitable for projection applications because of its high luminous efficacy. Furthermore, a substantially automated and accordingly cost-effective assembly of the lamp is possible.

The invention relates to a reflector lamp which is formed essentially bya light source, in particular in the form of a high-pressure gasdischarge lamp (HID [high intensity discharge] lamp or UHP [ultra highperformance] lamp), a main reflector (secondary reflector), and aprimary reflector by means of which light from the light source isreflected onto the main reflector.

Reflector lamps of this kind are used by preference inter alia forprojection purposes because of their optical properties and aredescribed, for example, in DE 101 51 267.8. Features essential for thisapplication are in particular a luminous efficacy which is as high aspossible and a radiation characteristic which is as even as possible inilluminating the projection surface.

A problem that may counteract an optimization of these properties isformed, for example, by fastening elements and/or lead-throughs for thelamp in the main reflector, which will have the result that the lightissuing from the light source is partly obscured and/or is incident onregions which are not reflecting or which have reflection propertieswhich adversely affect the radiation characteristic of the reflectorlamp.

It is useful in this connection to distinguish between the reflectorportion, which has a certain, optically active shape and supports themain reflector (reflecting layer), and a neck portion which servesprimarily for fastening the lamp and for passing through supply lines.The two portions form the reflector body which has a reflector openingor light emission opening.

During mounting, the lamp must be aligned in the reflector body inaccordance with the shape of the main reflector and then fixed in thecorrect position (for example with lamp cement) so as to achieve optimumoptical properties or a certain radiation characteristic.

The neck portion is dimensioned such that the accommodated lamp can becorrectly aligned. This must be done while taking into account on theone hand the manufacturing tolerances of the reflector body and the lampand on the other hand the fact that the actual light source, i.e. thedischarge arc in a discharge lamp, will not occupy an exactly definedand reproducible position in the discharge space for reasons ofmanufacturing technology. Therefore, the discharge arc must be broughtinto the focus of the reflector, i.e. into the optimum position, whilebeing optically checked and while the lamp is burning. This means thatthe diameter or opening of the neck portion must be so large thatsufficient space is available for adjusting the lamp.

It is also required, however, that the diameter of this neck portion,i.e. of the opening thereof, should be as small as possible for opticalreasons, so as not to lose too much of the surface area available forthe reflector. This is true in particular for the case in which the lampis inserted comparatively deeply into the reflector and thus comes veryclose to the rear end of the reflector. In a usual parabolic reflectorwith a focal distance of approximately 7.5 mm and a lamp whose dischargevessel has a diameter of approximately 9 mm, the discharge vessel willbe at a distance of no more than approximately 3 mm from the reflectorsurface. A comparatively large spatial angle of the light radiation isaccordingly associated with a comparatively small reflector surfacearea, so that a correspondingly large light loss may be occasionedthereby. It is for this reason that a maximum difference between thediameter of the rearmost opening in the reflector reserved for the lampand the diameter of the lamp is generally allowed to be approximately 1mm, so that the space available for mounting and adjustment is stillcomparatively small.

The required small opening of the neck portion also renders anautomation of the adjustment and mounting more difficult. The lamp mustbe held by its rear end so as to be capable of alignment in theoperational position, which means that the lamp must either beintroduced into the reflector body through the neck portion, which isusually not possible given the small neck portion diameter, or it mustbe gripped by its front end for inserting into the light emissionopening of the reflector and then gripped again by its rear end. Bothalternatives require a considerable mechanical expenditure, which isfurther increased by the introduction and the comparatively slow curingof the lamp cement.

A further problem is that the rearmost portion of the reflector body,and in particular of the reflector portion, may be manufactured with aless exact geometric shape than the front portion, which lies in theregion of the light emission window. The reason for this is that thewall thicknesses are greater in the rear portion of the reflector body,and that the neck portion and suitable fastening elements are also to beformed there. Such a geometric inaccuracy may be very disadvantageousbecause every irregularity in the rear reflector portion has acomparatively wide spatial angle associated with it, so that it has amuch stronger influence on the radiation characteristic than anirregularity in the front reflector portion.

The invention accordingly has for its object to provide a reflector lampof the kind mentioned in the opening paragraph whose optical propertiesare adversely affected to a substantially lower degree, or not at all,by said rear portions of the reflector portion and/or other objects inthe reflector portion.

Furthermore, the invention has for its object to provide a reflectorlamp which can be mounted and aligned automatically, and accordinglyinexpensively, with a comparatively small mechanical expenditure,without the necessity of choosing a construction in which a portion ofthe effective reflector surface is no longer available.

A further object is to provide a reflector lamp which can beminiaturized considerably more strongly without substantial light lossesthan is possible for known reflector lamps.

The object is achieved, according to claim 1, by means of a reflectorlamp with a light source, a main or secondary reflector, and at leastone primary reflector which is provided for an at least substantialreflection through the light source onto the main reflector of thoselight portions originating from the light source which propagate in thedirection of optically inactivated regions of the main reflector orregions of the main reflector obscured by other objects.

Optically inactivated regions are understood to be those regions whichhave no reflection properties or reflection properties which adverselyaffect the radiation characteristic of the reflector lamp, such as, forexample, the opening of a neck portion in the main reflector andpossibly an edge of this opening. The degree of reflection of said lightportions is then essentially dependent on the reflectivity of the chosenreflector material and on the accuracy of the shape and position of theprimary reflector.

A particular advantage of this solution is that the reflector lamp issuitable in particular for projection purposes, because the reflectionof the kind mentioned above does not appreciably increase the extent(i.e. substantially the width of the radiation characteristic) of thelight source, so that no adaptation problems will arise in the insertioninto a projection optical system, even if the primary reflector hascomparatively large dimensions.

Furthermore, the influence of optically inactivated regions on theradiation characteristic of the reflector lamp is at least largelyeliminated also if these regions (for example in the form of a neckportion) are made comparatively large in comparison with known reflectorlamps so as to render possible an automated mounting of a lampcomprising the light source, and/or to achieve a high degree ofminiaturization without substantial light losses by means of an at leastpartial positioning of the lamp in the neck portion, and/or to be ableto use mechanical fastening means for the lamp instead of lamp cement,which means have the further advantage that they enable a substantiallymore accurate, reliable, and secure fastening of the lamp.

Finally, a disadvantageous influence on the radiation characteristic byobjects in the region of the main reflector, such as, for example,fastening elements, cooling means, etc., can be avoided with theinvention in that a (possibly further) primary reflector is positionedso as to take account of the positions and dimensions of said objects.

The dependent claims relate to advantageous further embodiments of theinvention.

Claims 2 and 3 relate to optically inactivated regions or objects whoseadverse influences may be preferably eliminated.

The primary reflectors as defined in claims 4 and 5 can be manufacturedin a particularly simple, effective, and inexpensive manner.

The embodiments of claims 6 and 7 render possible a particularly highdegree of miniaturization of the reflector lamp according to theinvention, while the embodiment of claim 8 may be used to particularadvantage in projection applications because of the intensity andcomposition of the radiated light.

Further particulars, features, and advantages of the invention willbecome apparent from the following description of preferred embodiments,which is given with reference to the drawing, in which:

FIG. 1 is a diagrammatic longitudinal sectional view of a firstembodiment;

FIG. 2 is a diagrammatic longitudinal sectional view of a secondembodiment; and

FIG. 3 is a diagrammatic longitudinal sectional view of a thirdembodiment.

Identical or corresponding components have been given the same referencenumerals in FIGS. 1 to 3.

The reflector lamps according to the invention are composed of areflector body 1 and a lamp 2 each time, as can be seen from theseFigures.

The reflector body 1 comprises on the one hand the reflector portion 11which carries on its inner wall a reflector surface (main or secondaryreflector) 12 in the form of an optically reflecting layer. The innerwall is shaped such that the light of the lamp 2 issues from the lightemission opening of the reflector body 1 with a desired radiationcharacteristic. In general, this shape has a parabolic gradient(parabolic mirror), but ellipse-type and other shapes are alternativelypossible, which shapes are chosen in dependence on the nature of a beamgeneration required for a given application.

The optically reflecting layer is formed, for example, by a metal layeror by single or multiple dielectric layers lying on top of one another.

On the other hand, the reflector body 1 comprises a neck portion, whichserves essentially for accommodating and fixing the lamp 2, at its rearend opposite to the light emission opening.

The lamp 2 shown in the present case is a gas discharge lamp whichcomprises a burner 21 with a discharge space in which the arc dischargeconstituting the actual light source 22 is excited between twoelectrodes, as well as a first and a second lamp end 23, 24 throughwhich a supply current is introduced. At least the first lamp end 23extends through the neck portion 13 of the reflector body 1 for fixationof the lamp 2.

Alternatively, an incandescent lamp or some other light source may beused.

As can be seen in FIGS. 1 to 3, furthermore, the burner 21 of the lamp 2is provided at its surface with an optically reflecting layer (primaryreflector) 25 which, like the reflector surface 12, is formed, forexample, by a metal layer or a number of superimposed dielectric layers(multilayer dichroic filter), and which is provided by known coatingprocesses.

The layer or coating 25 here lies on the rearmost half of the burner 21,i.e. on the portion adjoining the opening of the neck portion 13, andextends in forward direction (in the direction of light radiation), forexample as shown in FIGS. 1 and 3, up to the “equator” of the burner 21,i.e. up to approximately the level of the geometric center of the lightsource 22 (arc discharge or incandescent coil).

This coating 25 thus renders the optical function of the rearmost orobscured portion of the reflector surface 12 at least substantiallyredundant. The negative influence of the comparatively low opticalquality of the rearmost portion of the reflector surface 12 on theradiation characteristic of the reflector lamp is thus also at leastsubstantially eliminated.

Among the results of this is that the size of the opening of the neckportion 13 is no longer critical with respect to the losses at thereflector surface 12 mentioned above, and may accordingly be made solarge in particular that the lamp 2 can be introduced into the reflectorbody 1 from behind, while sufficient space is available for itsalignment. This also opens up the possibility of an automated assemblyand adjustment with comparatively little expenditure.

Furthermore, the rear end of the reflector body 1 can also bedimensioned considerably more freely, so that, for example, suitablemechanically adjustable fastening elements can be used for the lamp 2instead of lamp cement.

The surface provided with the coating 25 is advantageously shaped suchthat the light originating from the light source 22 and incident on thecoating 25 is at least substantially reflected towards itself and isaccordingly aimed through the light source 22 onto the reflector surface12. This back reflection has the further advantage that the extension ofthe light source 22 is not increased by the reflection at the coating25, i.e. the radiation characteristic of the light source is notsubstantially widened, so that in particular in projection systems noadditional adaptation problems will arise in the insertion into theoptical projection system.

In the first embodiment of the invention shown in FIG. 1, the diameterof the neck portion 13 is dimensioned such that the lamp 2 can beadjusted and fastened with its first lamp end 23 therein in the requiredmanner, but in this case it is inserted into the neck portion inconventional manner through the light emission opening of the reflectorbody 1. The coating 25 in this embodiment extends on the surface of theburner 21 between the start of the first lamp end 23 situated in theneck portion 13 and approximately the “equator” of the burner 21, whichlies approximately at the level of the geometric center of the lightsource 22.

In the embodiments shown in FIGS. 2 and 3, the neck portion 13 has adiameter such that the lamp 2 can be inserted through this neck portion13, i.e. from behind into the reflector body 1.

In the second embodiment of FIG. 2, there is also a portion of theburner 21 situated inside the neck portion 13, and the reflectingcoating 25 extends from the start of the first lamp end 22 lying insidethe neck portion 13 only so far in the direction of the light emissionopening of the reflector body 1 that it optically replaces the openingof the neck portion 13 and possibly the region of the reflector surface12 immediately surrounding this opening, which region may haveinsufficient optical properties.

It also becomes apparent from these embodiments that the rear portion ofthe reflector surface 12, which surrounds the opening of the(comparatively narrow) neck portion 13, is optically no longer necessarybecause of the coating 25.

In the third embodiment shown in FIG. 3, it is not only the first lampend 22, but also approximately half the burner 21 which lies inside theneck portion 13 of the reflector body 1, such that the geometric(virtual) continuation of the reflector surface 12 extends through theburner 21.

The second and in particular the third embodiment have the furtheradvantage that the focal distance of the reflector portion 11 and thediameter of the burner 21 may be chosen substantially independently ofone another. This renders possible a further miniaturization of thereflector lamp for substantially the same light catchment efficiencycompared with known reflector lamps, in which the focal distance of thereflector portion 11 must be greater than the radius of the burner 21 soas to avoid light losses.

All embodiments furthermore provide the possibility of providing thereflecting coating 25 asymmetrically, and in particularnon-rotationally-symmetrically on the surface of the burner 21. This maybe useful in particular if further components such as, for example,mounting elements, lamp contacts, ignition aids such as antennas, orcooling devices, etc., are present inside the reflector body 1 next tothe lamp 2. In such a case the edge of the coating 25 could run suchthat said components are obscured, while the coating 25 reflects thelight back onto itself and aims it through the light source 22 onto thefree regions of the reflector surface 12.

Alternatively, a further primary reflector in the form of a localcoating on the burner surface may be arranged so as to correspond to thepositions and dimensions of these objects.

Preferred combinations of the primary and secondary reflectors aredisclosed in the cited publication DE 101 51 267.8, which isincorporated in the present disclosure by reference. Various reflectingcoatings and materials are described therein, from which materials thecoatings are preferably composed so as to achieve their desired opticalproperties (for example dichroically reflecting coatings) and to achievecoefficients of thermal expansion which correspond as closely aspossible to those of the material of the reflector portion 11 and theburner 21, as applicable. These materials are in particular SiO₂, TiO₂,and/or ZrO₂, and/or Ta₂O₅.

1. A reflector lamp with a light source (22), a main or secondaryreflector (12), and at least one primary reflector (25) which isprovided for an at least substantial reflection through the light source(22) onto the main reflector (12) of those light portions originatingfrom the light source (22) which propagate in the direction of opticallyinactivated regions of the main reflector (12) or regions of the mainreflector (12) obscured by other objects.
 2. A reflector lamp as claimedin claim 1, wherein said optically inactivated regions are formed by athrough passage in the main reflector (12) which is provided for a lamp(2) comprising the light source (22).
 3. A reflector lamp as claimed inclaim 1, wherein said objects are fastening means, cooling means,ignition means, or other means provided for activating and/or operatingthe light source (22).
 4. A reflector lamp as claimed in claim 1,wherein the primary reflector is formed by an optically reflectingcoating (25) which is provided on a surface of a lamp (2) comprising thelight source (22).
 5. A reflector lamp as claimed in claim 4, whereinthe optically reflecting coating (25) is formed by a metal layer or by aplurality of dielectric layers or dichroic filters.
 6. A reflector lampas claimed in claim 1, which comprises a reflector body (1) with areflector portion (11) supporting the main reflector (12) and a neckportion (13) for introducing a lamp (2) comprising the light source(22), such that the geometric continuation of the main reflector (12)passes through the burner (21) of the lamp (2).
 7. A reflector lamp asclaimed in claim 1, which comprises a reflector body (1) with areflector portion (11) supporting the main reflector (12) and a neckportion (13) for introducing a lamp (2) comprising the light source(22), such that the focal distance of the main reflector (12) is smallerthan the radius of the burner (21) of the accommodated lamp (2).
 8. Areflector lamp as claimed in claim 1, wherein the light source (22) isan arc discharge in a high-pressure gas discharge lamp (2).
 9. Aprojection system with at least one reflector lamp as claimed in claim1.